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View Full Version : Good source for 9.5:1 or 10:1 pistons for my 401


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Lifted79CJ7
02-21-2004, 12:00 AM
Anyone have any hook ups? I don't feel like dropping $675 on Venolia's. A little too far out of my budget. :smile: It will be press pins and 57.92 cc heads on a 1978 block. Anyone? Anyone? Bueller? Bueller?
:razz:
Jack

78304CJ-7
02-21-2004, 11:13 AM
If you want forged pistons you are kinda in a rut, I have a set of TRW 2382P .030 over that are good for 9.5:1 on the later heads. However at this moment they are going to Canada for use.

You might want to look into the Kieth Black Hyper pistons, they have introed a few new ones for the AMC 390/401 crowd.

http://www.kb-silvolite.com/performance.php?action=search&mfg=AMC&EngSize=401&RodLen=5.858

I have been thinking of going this way.

-RJ

Lifted79CJ7
02-22-2004, 08:59 PM
Nice! Daddy like! So I see one is for 9.5:1 with my heads and one is for 10.9:1. OK, so this leads me to a few questions.

1) That second piston is a little too high of a compression for pump 93 octane, isn't it? :-| This thing will be for a weekend run about vehicle, not a daily driver.

2) These pistons are cast, not forged, correct? So how do they hold up? :-|

3) What in the world does Hypereutechtic mean? (excuse the sp!) :-|

Oh, and FYI, Summit has the 9.5:1's for only $386.49. If these will work for 80K miles (keeping the engine under 5000rpm), then I am sold! :?
Jack

Lifted79CJ7
02-26-2004, 09:23 PM
OK, so my friend told me that hypereutetic pistons actually have a higher silicon content that other pistons, making them stronger. Don't know if this is true or not, but just thought I'd pass on the info to everone! Anyone else know of any additional info?

Jack

Tigger
02-26-2004, 09:45 PM
the Hypertectic pistons do have a have a higher silicon content and are stronger, however I have read that they are prone to breakage if exposed to NOS or engines with detonation problems.

78304CJ-7
02-27-2004, 12:41 PM
Hypers come in between cast and forged pistons. They KB are a nice pistons, but they are still not a drop in fit, they use a smaller chevy pin so you would have you have your rods setup for bushed pins. They do this for a few reasons, chevy pins are cheap, (many many more made then AMC 1" pins) Also, they are lighter reducing, so make sure when/if you use them you have your engine balanced, and actually if you are running anything other then stock pistons you should do this anyways.

-RJ

FSJnovice
02-29-2004, 02:22 PM
Hyperectic pistons are a good choice, when getting a set have the skirts of the pistons coated with (cannot remember if it is ceramic or teflon type item) they will last longer. They are also more forgiving under more than stock horsepower numbers. :t:

Lifted79CJ7
02-29-2004, 08:08 PM
Cool, thanks fo rall the help guys! I sent an email to KB about everything I heard here. I will keep ya updated with what I find out!
:t:

Oh, I borrowed this from Keith Blacks tech page:

"Hypereutectic -vs- Forged Pistons

Hypereutectic pistons are used in some original equipment engines. They are favored because of reduced scuffing, improved power, fuel economy and emissions.

Hypereutectic 390 refers to a unique aluminum piston alloy that contains dissolved and free silicon. The material can be T6 heat treated to high strength and stiffness. Non-heat treated 390 hypereutectic alloy aluminum has slightly less strength than conventionally cast F-132 aluminum.

With this in mind, we caution the reader about the use of non-T6 heat treated O.E. design hypereutectic pistons for high performance. Silvolite and others do make replacement-type hypereutectic pistons that are worthwhile for stock replacement applications. Original equipment design is almost never suitable for performance applications.

The KB line of hypereutectic pistons were designed around the 390 alloy. The result is a high performance part intended to give the performance engine builder access to the latest in piston technology.

Forgings have long been the mainstay of the performance business and did well in the big cubic inch engines of the 60’s. Now, with focus on peak cylinder pressure timing, ring sealing dynamics, cylinder air tumble and swirl, combustion chamber science, and extended RPM ranges, we need to consider some new piston options.

The KB T6 hypereutectics are considerably different than the forgings. The KB pistons have shown improvement in power, fuel economy, cylinder sealing, service life, and cost effectiveness. The reduced thermal expansion rate allows the piston to be run with reduced clearance. A tight piston is less likely to rock, make noise, and burn oil. A rocking piston wears rings and increases blow-bye. The close fit of the KB piston allows the piston rings to truly seal, minimizing blow-by.

The design flexibility enjoyed by the KB series of pistons has an advantage over present day forging practices. The die for a forged piston must be designed so it can be easily removed. This limitation makes it difficult to make a light weight piston without sacrificing strength.

The KB pistons' utilization of the permanent mold with multiple die parts allows undercut areas above the pin hole and material distribution in the skirt area that stiffen the entire piston unit. The forged piston requires thick skirts to achieve comparable piston rigidity. A rigid piston rocks less in the cylinder and improves ring seal.

The forged pistons' thick skirts add weight. The design of KB pistons gives us the option to build the lightest pistons on the market.

Some current KB pistons are not super light for several reasons. If the piston is to be used as a stock replacement, more than a 10% weight reduction will mandate that the engine be re-balanced.

Common sense suggests that the introduction of a new product be extra strong at the initial release. As the product becomes accepted, weight reductions are scheduled as regular product upgrades, as justified with actual race testing.

There will always be a market for custom forged pistons. Small runs of forgings are more economical than small runs of permanent mold pistons because of the complexity of permanent mold tooling. Where quantities justify, expect to see future KB pistons developed that are lighter and stronger than anything else on the market. Machined head profiles are easily changed with our CNC equipment so we will stay current with new cylinder head developments. Volume production is expected to keep the price reasonable.

Our pricing policy has given the impression to some that we are building an economy, or in between, piston. The truth is, we are striving to build the "State of the Art" piston that is best, regardless of price. Reasonable pricing is just an added benefit."


Jack

Lifted79CJ7
03-04-2004, 04:36 PM
OK, so I called Keith Black today about the KB354 (9.5:1 compression ratio pistons) and asked if you have to run Chevy pins, or if you can order them for stock AMC pins. Looks like you can only get them for Chevy pins. Dang it! Doesn't make much sense. :-| You can buy a piston for cheaper than customs forged, but you have to have a crap load of machine work done and buy even more parts to get hem to work. Doesn't make sense to me. 111!!! Not sure what to do now. Guess I am gonna just keep on hunting for some pistons. Dang it, and I though I had it all figured out. :(: Oh well, I am gonna go start drinking now. :razz: Anyone have any advise? I don't want to pay the local machine shop $180 to get the pistons to work, plus have to buy new pins. Arrrgghhhh!!
Jack

Gremlin4ever
04-03-2005, 09:42 AM
OK, so I called Keith Black today about the KB354 (9.5:1 compression ratio pistons) and asked if you have to run Chevy pins, or if you can order them for stock AMC pins. Looks like you can only get them for Chevy pins. Dang it! Doesn't make much sense. :-| You can buy a piston for cheaper than customs forged, but you have to have a crap load of machine work done and buy even more parts to get hem to work. Doesn't make sense to me. 111!!! Not sure what to do now. Guess I am gonna just keep on hunting for some pistons. Dang it, and I though I had it all figured out. :(: Oh well, I am gonna go start drinking now. :razz: Anyone have any advise? I don't want to pay the local machine shop $180 to get the pistons to work, plus have to buy new pins. Arrrgghhhh!!
Jack

The deal is that it is "cheaper" for KB to sell you chevy pistons and you custom fit them to your motor than it is for KB to retool to make a line of pistons that there realy is no market for. 80% of the market is chevy and we fall under the other 20% I was told, but I really know AMC is probably just 1% if that much. :smile:

jeepmonster
04-05-2005, 07:41 PM
. "The reduced thermal expansion rate allows the piston to be run with reduced clearance. A tight piston is less likely to rock, make noise, and burn oil. A rocking piston wears rings and increases blow-bye. The close fit of the KB piston allows the piston rings to truly seal, minimizing blow-by"


This is why I think forged pistons are not often the best route to go with in a mild perfromance build up. Cast pistons can be fitted with much closer tolerances in the cyinder and therefore seal better and fit better and "rock" less and they dont run as hot, all of that = more power over forged. The FACT, is that if the motor is tuned to eliminate detonation(i.e.; "tuned properly" :roll: ) forged pistons are overkill. The stock AMC CAST pistons are good for 6000 RPM all day long( Ask me how I know; my 74,000 original mile 343 factory pistons looked great, after years of running on 89-94 octane) and modern stock cast replacements are going to be better than the OE anyway. Almost all the muscle cars had cast pistons and many still have the orignals pumping their cylinders. Don't bother with forged unless you are going to drage race with 12.5 :01 compression and 100 shot of nitrous.
For a normally aspirated 10 :01 compression motor that isnt going to see over 6000 RPM cast is fine and probably has more advatages over a forged at that level. A lot of people convince themselves that they need forged or that forged are better for their performance level when in fact they are not. :t:

FSJer
07-25-2005, 02:23 AM
check out www.FlatlanderRacing.com , these guys sell heaps of parts for Hi-performance motors , heaps of stuff for AMC. They - which i will probably get ( less i can get a 401 builder ) custom forged Wiseco pistons for around $499 a set with pins & locks , which is damn cheap for these . you can get them in any size , any compression ratio which is cool. they have heaPS of other stuff too.

Lifted79CJ7
07-25-2005, 05:20 PM
Yeah, I have learned quite a bit over the last year. Course moving 3 times kinda sets ya back financially. Hopefully by the end of this year I will be good to go...

tufcj
07-25-2005, 05:58 PM
www.fastengineparts.com sells Ross forged pistons for the 401. I think they advertise about 10.5 with the 291C heads, about 9.8 with the later 58cc heads. These fit the stock AMC rod. They list on the web site for about $675 a set, but watch ebay, they list there for about $550. You can call, and they'll give you the ebay price. They also list the KB pistons there, I didn't pay attention to the price.

I have a set of the Ross pistons in my 390. So far, I'm very happy with them.

Bob
tufcj

Lifted79CJ7
07-25-2005, 07:00 PM
Yeah, I have been watching them - That is probably who I will buy from - good prices. They just weren't really around with the AMC pistons on ebay when I started this thread. Glad they are supporting us more now, though!!!

78304CJ-7
07-26-2005, 07:44 AM
check out www.FlatlanderRacing.com , these guys sell heaps of parts for Hi-performance motors , heaps of stuff for AMC. They - which i will probably get ( less i can get a 401 builder ) custom forged Wiseco pistons for around $499 a set with pins & locks , which is damn cheap for these . you can get them in any size , any compression ratio which is cool. they have heaPS of other stuff too.

I was looking atht eFlatlanderracing Wiseco pistons, http://www.flatlanderracing.com/flatpistons-amc.html

they show the only bore is .035. Not that is a stange overbore if you ask me 111!!!

Also they look to be 629.00 now :-|

-RJ

FSJer
07-27-2005, 05:55 AM
Only problem is that the stock cast piston with 58cc heads ( most people have these heads ) is only around 9.0:! , do you know of anyone who sells a cast or hyper 10.0:1 compression piston for a 360 ?? i have searched all over the web and i can't find "ONE" set of higher compression pistons in cast or hyper for a 360 ? for someone seeking a higher compression piston other than stock ( 9.0:1 )- then i'd say go forged ! also quality forged pistons of this era can run alot tighter clearances than 40 years ago.

FSJer
07-27-2005, 06:00 AM
I rang flatlanderracing a week ago and asked about pistons and i was told they can customize the pistons you want in any size and any compression ratio ( sounds awesome ) for $499 for wiseco forged. not sure whats goin on there.

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